An object of our invention is to provide a needle assembly for a phonograph pickup cartridge which provides for selective adjustment or setting of operative sensitivity and compliance to different selected values, to thereby replace the need for manufacture and stocking of a plurality of cartriges having different sensitivities or compliances to suit a predetermined preference.
We are aware of needle assemblies which are commercially referred to as TETRAD assemblies, wherein needle shanks of different lengths are provided for assembly with the shank holder and cartridge drive member and wherein needle shank length represented a predetermined sensitivity and compliance. Since needles are very small, it is difficult for the ordinary person, without special tools, to properly assemble a needle with its holder. Further, a manufacturer was required to produce, and a dealer was required to stock, needles in a pluraltiy of lengths, and certain lengths may be sold faster then others, thus producing an imbalance in stock which constantly required close attention.
Our invention overcomes the above-noted difficulties in that in our improved assembly only one needle shank length is required. By adjustment of the needle shank relative to the drive member along the longitudinal axis of the cartridge, the needle lever ratio is changed to provide for changes in compliance and sensitivity.
We are also aware of U.S. Pat. No. 3,531,601, issued Sept. 29, 1970, to Richard P, Muttick. In this patent, a two-section or two-part phonograph cartridge is required. One part, designated as the transducer mounting structure, carries the mechanoelectric transducer and associated elements, including the transducer and associated elements, and transducer to stylus coupler. The other cartridge part, designated as the cartridge mounting structure, is attachable to the tone arm. In the Muttick patent, the transducer mounting structure is adapted to be guided by the fixed cartridge mount along a guideway on the latter, to a plurality of longitudinally displaced positions. This required a high degree of accuracy in the guideway, and a movement of masses, not necessary in our improved needle assembly.
Our invention requires movement of only one part of low mass and since such part directly carries the needle shank and tip (or tips), accuracy in the adjustment for compliance and sensitivity is improved.